Dispenser

ABSTRACT

The invention provides an air treatment device comprising: an airborne agent detector comprising a plurality of airborne agent sensors, wherein the airborne agent detector comprises means to detect a threshold level or concentration of an airborne agent; a means to mount a source of air treatment agent to the device; and a means to expel a portion of air treatment agent from a mounted source of agent, upon detection of an airborne agent by the detector.

The present invention relates to a dispenser for air treatment agents,especially for use in deodorising or neutralising odours in an airspace.

Air fresheners and other air treatment agents are widely used in manyapplications, in houses, vehicles and elsewhere. Although they areusually refillable, or cheap and disposable, it is inconvenient to haveto fill or replace them often, particularly when many such items are inuse for example in a large building. It is also an inconvenience tomonitor levels within the devices in order to order refills or new stockas and when the devices become depleted. Furthermore, it can be wastefulto have such devices emitting when not needed.

It would therefore be desirable to extend the life of a substance to bedispensed in an air freshener or odour neutraliser, such as a fragrancefor example, in order to reduce costs. One way of extending a life of anair freshener is to include a lid or closure substantially sealing theair freshener to prevent release of the active agents, until a useropens the lid. However, clearly this is inconvenient for the user, andagain if a user forgets to re-close the lid after use, unwanted releaseof the active agents will continue until the device is depleted.

Automated versions of this idea have been proposed, in which adispensing mechanism turns on and off periodically; set by a user. Thesesystems are adequate when it is possible to predict when dispensing ofthe active agents is needed; but is inadequate if for example malodouror other substances enter an atmosphere at non-regular intervals.

Efforts have been made to design an air freshener, which dispensesfragrance, deodorant or sanitizing agent only when a room is occupied,and which utilises infrared detectors to detect movement within a roomor air space. However, it is rarely necessary to dispense the activeingredient when a person is present in the room, unless said person hasundertaken activity, which produced malodour or undesired odours. Thusinfrared detection and subsequent release of active ingredient can berelatively wasteful, inefficient and expensive.

The need for efficient non-regular or regular release of air fresheneris equally applicable to other active ingredients such as odourneutralisers, anti-bacterial agents, and anti-allergenic compounds; forexample if there is a high pollen count within an enclosed space, inorder to prevent a person suffering from hay fever from showing symptomsof their predicament. Other allergens include fungal spores, dust mites(and their droppings), pet allergens and the like, for example.

JP 2001 087370 discloses a deodoriser with spraying means forneutralising acid and alkaline odour components when detected by odoursensors.

It would therefore be advantageous to provide an active ingredientrelease mechanism, which allows portions of air treatment agent to bereleased from a device only as and when a particular stimulus is presentin the air space around the device or within an enclosed space, andwhich avoids ingredient release as the result of false detection ofstimulus.

A problem with devices triggered by very low levels of airborne agent,such as may be detected by the human nose, is that such devices areprone to false detection and triggering, thus wasting the air treatmentagent.

Another problem is that such devices may trigger when no humans arepresent, and so again the air treatment agent may be wasted.

It would also be advantageous to improve the efficiency of release ofair treatment agents from devices, into airspaces, in particularmaximising the distribution of the agent and enabling release in theoptimum efficient manner in response to stimuli in the airspace, or lackof the stimuli. It would also be advantageous to provide an airtreatment agent device which is not a line-of-sight device, and whichwould not be triggered to release an air treatment agent by stimuliother than desired stimuli for said device.

It is the aim of preferred embodiments of the present invention toovercome or mitigate at least one problem of the prior art, whetherexpressly disclosed herein or not.

According to a first aspect of the invention there is provided an airtreatment device comprising: an airborne agent detector comprising aplurality of airborne agent sensors, wherein the airborne agent detectorcomprises means to detect a threshold level or concentration of anairborne agent; a means to mount a source of air treatment agent to thedevice; and a means to expel a portion of air treatment agent from amounted source of agent, upon detection of an airborne agent by thedetector.

Preferably the airborne agent detector is of a type whose electricalconductivity is altered, by exposure to the airborne agent.

Preferably the threshold level is at least 0.1 ppm by volume of air ofthe target airborne agent, more preferably 0.05 ppm, even morepreferably 0.01 ppm

Preferably said source is a single source of a target airborne agent.

The device may be of a type in which air treatment agent is expelledonly in response to the detection of an airborne agent.

The device may be of a type in which the expulsion of air treatmentagent in response to the detection of an airborne agent is not the onlyway in which air treatment agent is expelled. For example air treatmentagent may be passively emanated, and on detection of an airborne agent,an additional portion of air treatment agent is expelled to supplementthe background level of passively emanated airborne agent. This may beachieved by various means, for example by expelling a pulse of airtreatment agent using a pumping device, or preferably by use of a fanwhich accelerates the rate of release of the air treatment agent fromthe passive emanator. In another embodiment, a heater element inproximity to a diffusion wick may be actuated in order to increase theemanation of the air treatment agent.

By airborne agent is meant an airborne chemical in the form of a gas,vapour,solid or liquid particle or droplet.

Suitably the airborne agent detector is operably connected to the meansto expel a pulse of air treatment agent, such that the portion of airtreatment agent is triggered in response to an airborne agent beingdetected by the detector.

The means to mount a source of air treatment agent to the device maycomprise means to connect a receptacle to the device, the receptaclecomprising the air treatment agent. The means to mount a source of airtreatment agent may comprise a clip, retaining member, catch, flange,bracket or other similar structure, capable of cooperating with anagent-filled receptacle, and more preferably capable of releasablymounting the agent-filled receptacle.

The portion of air treatment agent may be a pulse of air treatmentagent. The portion may be a single pulse. The portion may be acontinuous stream of agent over a defined time period, or a plurality ofintermittent pulses or streams of agent over a time period which may bepre-determined or be controlled by the device itself and related to thedetected level of airborne agent.

The device may be arranged to expel a background level of air treatmentagent which may be continuous or intermittent, and the portion of airtreatment agent may comprise a booster portion of agent expelled by thedevice upon detection of an airborne agent by the detector. Thus, forexample the device may utilise as an air treatment agent, a deodorant,which may be expelled continuously at a low level to provide constantdeodorising action, and upon detection of an airborne agent by thedetector, the device may be effected to expel a booster portion of thedeodorant to counteract the detected airborne agent. The device may thenreturn to expelling a continuous background level of agent when thedetector detects no further airborne agent, or detects an airborne agentunder a minimum threshold concentration.

The airborne agent detector may comprise means to detect a singleairborne agent or a mixture of airborne agents. The airborne agentdetector may comprise means for a user to input which airborne agent oragents the detector is arranged to detect, in use.

The airborne agent detector may comprise means to detect a thresholdlevel of an airborne agent or agents. The expulsion means may only beactivated upon detection of the defined threshold, such as a thresholdconcentration, of an airborne agent, which threshold may be user set orfactory set, for example. Thus, only upon detecting said threshold, thedetector may operably cooperate with the means to expel a portion of theair treatment agent from the device to activate expulsion of a portionof the air treatment agent.

The expulsion means may continue to expel the portion or a plurality ofportions of air treatment agent, until the detector no longer detects anairborne agent or a threshold level of airborne agent.

The dose of air treatment agent expelled is preferably related to thedetected level of airborn agent. For instance the dose of air treatmentagent released may be proportional to the level of airborne agentdetected. For instance the time over which expulsion of airborne agenttakes place may be linked to the level of airborne agent detected.

Preferably the airborne agent detector is a gas detector. Thus,preferably the gas detector is arranged to detect a gas and effectexpulsion of the portion of air treatment agent from the device inresponse to detection of the gas.

The gas detector may comprise one or more electronically conductive gassensors and/or one or more semi-conductive gas sensors.

Preferably the detector comprises one or more semi-conductive sensors.

The gas detector may comprise a plurality of sensors, each sensorcomprising a different sensor material. Preferably the gas detectorcomprises at least 3 sensors, preferably at least 4 sensors, each sensorcomprising a different sensor material.

In one embodiment the airborne agent detector is adapted to detectsulphur-containing gases; preferably at least one of hydrogen sulphide,methanethiol (also known as methyl mercaptan) and dimethyl sulphide;more preferably at least two of these; and most preferably all three.

In one embodiment the airborne agent detector is adapted to detectnitrogen-containing gases, preferably at least one of ammonia andnitrogen dioxide, preferably both of these.

In one embodiment the airborne agent detector is adapted to detectcarbon monoxide.

The airborne agent detector may be adapted to detect at least two, andpreferably all three, of sulfur-containing gases; nitrogen-containinggases; and carbon monoxide.

Useful as semiconductor gas sensors are those gas sensors comprising ametal oxide. Thus preferably the gas detector comprises at least onemetal oxide gas sensor, hereinafter referred to as “MOX” gas sensors.

Semi-conducting MOX sensors, heated to approximately 300° C. in air areknown to exhibit a strong sensitivity to traces of reactive gasespresent in the air. The sensitivity is translated into resistance changedue to loss or gain of electrons as a result of the target gas reactingwith oxygen. The loss or gain of electrons can thus be measured andcorrelated to determine which gases are present in the air. Thus theloss or gain of electrons can be measured quantitatively as themagnitude of change in electrical resistance, and thus correlates to theconcentration of target gas present around the sensor.

Suitable MOX gas sensors include gas sensors comprising oxides oftungsten, tin, any suitable semi conducting metal oxides, such as thosecomprising zinc, titanium, chromium, cobalt, molybdenum and vanadium,for example.

Particularly preferred MOX gas sensors include sensors comprising one ormore of the following metal oxides: SnO₂, WO₃, Cr_(2−x)Ti_(x)O_(3+z)(where x is from 0.1 to 0.8 and z is determined by the level ofvacancies in the material, which is non-stoichiometric: preferably x isfrom 0.1 to 0.3), TiO₂, ZnO₂, MoO₃ and V₂O₅. The chemical formulae areindicative, as would be known to those in the art, because of thenon-stoichiometry of the oxides.

The gas detector may comprise at least one n-type MOX sensor and atleast one p-type MOX sensor.

Suitably the MOX sensor comprises a porous film or layer. Since thechange in electrical resistance in the sensing electrode is carried by asurface reaction, it is advantageous to maximise the surface area tointensify the response to gas.

Preferably the MOX sensor comprises a metal oxide material connected toa substrate or chip, more preferably an aluminium or silicon substrateor chip. The MOX material is preferably connected to an electrodematerial, such as platinum or tantalum or a mixture thereof, forexample. The electrode material may be inter-digital with the MOXmaterial or may be connected by any other suitable orientation orconfiguration. There may be an insulating layer on top of the substrate,such as, for example, an oxide layer of the silicon or aluminiumsubstrate between said substrate and said MOX material.

The MOX sensor may also comprise a means for heating the sensor to arequired temperature. The means for heating the sensor may comprise ametal member connected to the MOX material and operably connected to aheating means, such as an electrical heating element. The metal membermay comprise the same material on the electrode material, where present,and may thus be, for example, platinum or tantalum. The MOX sensor maybe heated, in use, to a temperature of at least 300° C.

In particularly preferred embodiments, the MOX sensor comprises asubstrate, preferably Si or Al, an oxide layer of the substratematerial, a MOX layer comprising inter-digital electrodes, a heatingmember comprising the electrode material and a temperature sensor.

The MOX sensor may comprise one or more additives to increase theselectivity and/or sensitivity of the MOX material to a particular gasor gases. The additive may be a catalytic additive such as platinum,palladium, gold or titanium, or activated carbon filters, for example.Particularly preferred sensors for detection of sulfur-containingairborne agents are SnO₂ with Platinum and Cr_(2−x)Ti_(x)O_(3+z)

The MOX sensors may comprise one or more protective coating layersarranged to prevent ablation or damage to the MOX material, in use. Theprotective coating layer may comprise a membrane, a sintered metal,carbon filter and the like, but the protective coating should notprevent charge transfer on the MOX sensor surface so preferably does notcover the active sensor material.

The gas detector may comprise a conducting polymer (CP) sensor, as analternative to, or in addition to a MOX sensor.

There are a number of potential advantages in using conducting polymers,over the other sensor technologies, for vapour and gas sensing. There isa far wider choice of materials and hence functional groups with whichthe gas or vapour can interact, and the materials are often easier toprocess than inorganic materials, i.e. metal oxides.

Some conducting polymer sensors can operate at room temperature, whichis a distinct advantage over the semiconductor sensing technique, asthere is a low power requirement. They also show reversiblecharacteristics at room temperature, this means that the recovery rateof the sensors after exposure to target compounds is better than SAW(Surface Acoustic Wave) sensors. The electronic control of the sensor isfar less complicated than both semiconductor, MOX and SAW (SurfaceAcoustic Wave) detection. The CP sensor is stable up to 40° C. and 90%humidity, which is the most significant advantage over the other sensingtechniques. Conducting polymer sensors may comprise two goldmicroelectrodes with an insulating gap between them. The conductingpolymer is grown electrochemically across the gap to form a sensor. Theconductivity of the polymer is altered by the presence of nucleophilicand electrophilic gases which results in a decrease and increase in theconductivity respectively. Therefore by following the resistance betweenthe two microelectrodes the sensors can be used to sense gases andvapours. The polymers may be doped with anions such as Cl⁻ and SO₄ ²⁻which can alter the sensitivity and/or selectivity to different vapours.

Suitable polymers for use in CP sensors include polypyrrole,polyaniline, polythiophene, polypyrorolidone, polyacetylene,polyaraphenylene, polyphthalocyanine, carbon black (or other carbonpolymers).

Other sensors that may be used in the gas detector include SAW (surfaceacoustic wave) sensors, electrochemical cells, optical gas sensors,GASFETS (Gas Field Effect Transistors) pellistors, fibre optic gassensors, and the like for example.

A gas detector is not a ‘line-of-sight’ detector and is not sensitive tolocation or orientation. Accordingly the device can be positioned in anout-of-the-way or unobtrusive location without affecting its operation.

In order to prevent a ‘false positive’ detection of gas by a detector,in which a gas similar to that which is arranged to be detected wouldtrigger a release of the air-treatment agent, the gas detector maycomprise a plurality of different gas sensors, each of which mustpreferably detect a specific gas before the air-treatment agent pulsecan be released. The plurality of gas sensors may comprise sensors ofdifferent materials, each of which may be arranged, to detect the samegas or different gases. Thus, for example the gas detector may comprisean array of metal oxide sensors of different materials, each of whichproduce a different signal in response to the same gas, and only when adefined combination of signals is emitted by the plurality of detectorswill the air treatment agent be released.

Alternatively or additionally some or all of the gas sensors may bearranged to detect different gases and the air treatment agent may onlybe released when a certain number or concentration of gases is detected.

Alternatively the airborne agent detector may comprise a biosensor orchemical sensor, arranged in use to detect an airborne agent which maybe a gas, liquid (including a vapour) or particulate solid.

The biosensor or chemical sensor may be arranged to detect an airborneparticle of biological material such as pollen, an allergenic protein,fungal spores, micro organisms, other proteins and the like, forexample, or an airborne chemical.

The device may comprise its own power source, such as one or morebatteries, for example, or solar cells. Alternatively the device maycomprise a plug or socket, arranged in use to cooperate with acorresponding electrical plug or socket, of for example, a mainselectricity supply.

Some detectors such as gas sensors, chemical sensors and biosensorsgenerally may have a low power requirement, and therefore a device ofthe invention using such detectors may be suitable as a portable deviceutilising an internal power source such as a battery, for example.

The device may include a processor unit which receives the signal(s)produced in response to the airborne agent(s), and determines whetherair treatment agent is emitted.

The device may include a person sensor, for example an infra-red sensor(e.g. a PIR sensor). The processor unit may be programmed such that onlywhen a person is present, is the air treatment agent emitted, and onlythen, in response to the sensing of a target airborne agent.

The processor may be programmed to cause release of air treatment agentonly when a sulfur-containing compound is detected.

The processor may be programmed to cause release of air treatment agentonly when a nitrogen-containing compound is detected.

The processor may be programmed to cause release of air treatment agentonly when carbon monoxide is detected.

The processor may be programmed to cause release of airborne treatmentagent when two, or preferably three, of a sulfur-containing compound, anitrogen-containing compound and carbon monoxide is detected.

The processor may be programmed to cause release of airborne treatmentagent only when a sulfur-containing compound is not detected (but whenanother airborne agent is present).

The processor may be programmed to cause release of airborne treatmentagent only when a nitrogen-containing compound is not detected (but whenanother airborne agent is present, to cause the release of the airbornetreatment agent).

The processor may be programmed to cause release of airborne treatmentagent only when carbon monoxide is not detected (but when anotherairborne agent is present, to cause the release of the airbornetreatment agent).

The processor may be programmed to cause release of airborne treatmentagent only when two of said types of airborne agents are not detected(but when the other type of airborne agent is detected, to cause therelease of the airborne treatment agent).

The device may include a timer, such that when the or each detector orsensor detects an airborne agent, air treatment agent is dispensed as acontinuous stream for defined period of time, and/or dispensed in adefined number of intermittent pulses. Intermittent pulses may be atregular time intervals or irregular time intervals.

The airborne agent detector, or detectors may be provided with a ASIC(Application Specific Integrated Circuit) circuit as the processor unit,to provide the necessary signals to the air treatment agent dispensingmeans, in order to activate said dispensing means.

The air treatment agent may be housed in any suitable receptacle, suchas a canister, bottle or vial, for example. The receptacle may be apressurised container such as an aerosol can for example, and may thuscomprise, in addition to the air treatment agent, a pressurised gas,preferably a hydrocarbon gas (or hydrocarbon which is a gas at ambienttemperature and pressure) such as propane, butane, or pentane, forexample, or a halocarbon gas, such as chlorofluorocarbon gases.

The receptacle may be detachably mountable to the device. Thus when thereceptacle becomes empty of air treatment agent the receptacle may beremoved and either refilled, or another agent filled receptacle mountedon the device.

The air treatment agent expulsion means may comprise any suitable means,such as a pump or aerosol for example, as are known to those skilled inthe art. The dispensing means may include a nozzle. The nozzle maycomprise an aperture, such as a circular or elliptical hole, or anelongate slot, for example. The nozzle may comprise a plurality ofapertures, such as a spray head for example. The plurality of aperturesmay comprise a mesh.

The expulsion means may simply comprise a wick to enable evaporation ofan air treatment agent from the device. Alternatively the expulsionmeans may comprise ultrasonic expulsion means, nebulising means,electrostatic discharge means and the like, for example.

The nozzle preferably enables the air treatment agent to be dispensed asa spray or fine mist, which may be effected by forcing the agent througha plurality of restricted size apertures, or the like, for example.

The air treatment agent preferably comprises an agent capable ofmasking, neutralising or retarding malodour, or unwanted odour in anairspace around the device. The air treatment agent may comprise adeodorant, an anti-bacterial agent, a sanitizing agent, a fragrance or aperfume, for example. The air treatment agent may comprise ananti-allergenic material, preferably arranged to react with and/orneutralise an allergen detected by the airborne agent detector, in use.

The air treatment agent may comprise a solid in the form of granules orpowder, but preferably comprises a liquid or gas, at ambient temperatureand pressure. Preferably the air treatment agent comprises a liquid,which may be dispensed in the form of a fine spray or mist through asuitable nozzle. If the air treatment comprises a gas or liquid, it maycomprise a gas or vapour capable of reacting with the airborne agent tobe detected in order to neutralise any malodour associated with theairborne agent.

By gas detector we mean a detector capable of detecting a gas or vapourper se, and/or fine particulate solids or liquid droplets dispersed ingases or air.

The device may comprise a fan or similar means, operably connected tothe air treatment agent dispensing means. The fan may comprise part ofthe means to expel a portion of air treatment. The fan is preferablyarranged to activate immediately prior to and/or during activation ofthe dispensing means, in order to effect increased speed of expulsion ofthe air treatment agent from the device, and/or to increase thedistribution of the agent in the airspace surrounding the device.

The fan is preferably operably connected to the airborne agent detector,such that, upon detection of the airborne agent by the detector, the fanis activated prior to or during activation of the expulsion means.

The device may comprise a heater, operably connected to the airtreatment agent dispersing means. The heater may be arranged to activateimmediately prior to and/or during activation of the air treatment agentexpulsion means, in order to effect heating of the portion of airtreatment agent as it is expelled from the device. Thus the heater maybe used to vaporise, or render more fluid, a portion of air treatmentagent expelled from the device.

The heater may be arranged to heat the portion when said portion iswithin the device or agent receptacle; alternatively the heater may bearranged to heat the portion as it leaves the device. The heat may alsoserve to improve distribution of the air treatment agent throughconvection and may activate the air treatment agent molecules, if theair treatment agent comprises a composition which can be activated byheat, or which effects increased efficacy on heating.

The device may include an alarm, operable when a gas is sensed which isdangerous. For example the device may have an alarm triggered by athreshold level of carbon monoxide.

According to a second aspect of the invention there is provided a deviceof the first aspect of the invention on which is mounted a source of airtreatment agent.

According to a third aspect of the invention there is provided a methodof treating an airspace with an air treatment agent, the methodcomprising the steps of detecting an airborne agent in an airspace andactivating expulsion of an air treatment agent into the airspace inresponse to detection of the airborne agent.

The method may comprise providing an airborne agent detector, a sourceof air treatment agent and a means to expel a portion of air treatmentagent means upon detection of an airborne agent by the detector.

The method may comprise expelling a single portion of agent in responseto detection of an airborne agent, or may comprise dispensing aplurality of portions intermittently, whether at regular or irregularintervals. Alternatively the expulsion of agent may comprise expelling acontinuous stream of agent for a defined time period upon detection ofgas. The expulsion means may expel a continuous portion or intermittentportions of agent for as long as the detector detects an airborne or adefined threshold level of an airborne agent, or for a shorter or longerperiod of time, for example.

The portion(s) may be dispensed as a pulse of agent from the dispensingmeans.

For example, in the case of the detector detecting a gas produced bytobacco smoking, or a mixture of gases, the expulsion means may beeffected to expel a single portion of air treatment agent, or may beeffected to expel a plurality of portions for a defined time period orfor such a time as the detector continues to detect the gas or gases. Insome embodiments the expulsion means may also be arranged to expel oneor more portions of agent when the gas detector signals that no morefurther gas has been detected.

Alternatively, the expulsion means may dispense the portion continuouslyover a defined period of time, which period of time may be predefined bya user, or may correspond to a time period shorter than, equal to orlonger than the time period during which the airborne agent detectordetects an airborne agent or defined threshold level of an airborneagent.

Preferably the method comprises treating an airspace within a room,whether domestically (such as a kitchen, living room, bathroom, bedroom,toilet, garage, basement, loft, etc) commercially, or industrially. Themethod may comprise treating an airspace within an object, whether aclosed object or an open object. Suitable objects include dishwashers,washing machines, dustbins and other waste receptacles, wardrobes,laundry baskets, bags, shoes, vehicle interiors, refrigerators,cupboards, toilets, sanitary bins, nappy containers, sharps bins, andthe like for example.

The airborne agent detector, air treatment agent expulsion means, andsource of air treatment agent may be as described for the first aspectof the invention.

According to a fourth aspect of the present invention there is providedthe method of the third aspect using the device of the first or secondaspect.

For better understanding of the invention and to exemplify howembodiments of the same may be put into effect, the invention will nowbe described by way of example with reference to the accompanyingdrawings in which:

FIG. 1 illustrates a schematic view of a dispenser in accordance withthe invention;

FIG. 2 illustrates a plan view of the MOX sensor of the device shown inFIG. 1;

FIG. 3 illustrates a side sectional view of one of the MOX sensors ofthe MOX sensor array shown in FIG. 2;

FIG. 4 shows the results of an experiment using the device of FIGS. 1 to3, including MOX gas sensors, in simulated domestic conditions to sensegases produced by tobacco smoking;

FIG. 5 shows the results of a second experiment using the device ofFIGS. 1 to 3, in simulated domestic conditions; and

FIGS. 6 to 8 show the results of further experiments, withsulfur-containing gases.

We refer firstly to FIG. 1 which illustrates a side sectional schematicview of an air treatment dispensing device 2 the invention.

The device comprises a housing 4 on which is located an airborne agentdetector in the form of a gas detector, comprising a gas sensor array 6.Within the housing 4 is located a source of air treatment agent in theform a detachable canister 8 which comprises a liquid deodorant as anair treatment agent. The canister 8 is in electronic communication withthe sensor array 6 via an electrical circuit 7. The canister 8 comprisesan outlet conduit 11, at the end of which opens to a nozzle 10 whichcomprises a plurality of apertures (not shown) which enable deodorant toexit the housing 4 as a fine spray or mist, when the device 2 is used.Situated within the nozzle 10 is a fan 14, through which the outletconduit 11 extends. The fan 14 is arranged in use to be actuated uponexpulsion of a portion of deodorant from the outlet conduit 12 into thenozzle 10, in order to that the expelled portion is forced through theapertures of the nozzle 10, in order to increase distribution of thefine spray of mist outside of the device 2.

We turn now to FIGS. 2 and 3, which illustrate a front view and sidesectional view of the sensor array 6 of FIG. 1. The sensor array 6comprises a substrate 13 comprising a silicon base 14 as shown in FIG. 3on which is laid an insulating SiO₂ layer 16 as shown in FIG. 3. On topof the SiO₂ layer are positioned four metal oxide (MOX) sensors 12, 12′,12″, 12′″. The four MOX sensors 12, 12′, 12″, 12′″ comprise materials20: SnO₂, SnO₂/Pt, SnO₂ and SnO₂/Pt respectively.

Each MOX sensor 12, 12′, 12″, 12′″ further comprises its own abuttingunderlayer portion of the silicon substrate 14 and SiO₂ layer 16, andtwo spaced apart platinum electrodes 18, 18′, the span of which isbridged by the MOX sensor material 20. The electrodes are connected to avoltmeter 24 which can determine resistance across the sensor materialof the sensors 12, 12′, 12″ and 12′″, via electrical wires 22.

Each of the MOX sensors 12, 12′, 12″, 12′″, is operably connected to aheating member in the form of a Ta/Pt resistance layer connected to thesensor material 20 of the four sensor array 6 and which contacts each ofthe four MOX sensors.

Use of the device 2, will now be described with reference to FIGS. 1 to3 and FIGS. 4 and 5.

It is known that semi-conducting MOX sensors heated to approximately300° C. in air, exhibit strong sensitivity to traces of reactive gasespresent in the air. The measurement effect is commercially exploited foronly a relatively few number of oxides due to the requirement for aunique combination of resistivity, magnitude of resistance change in aspecific gas (sensitivity) and humidity effects. Amongst the oxideswhich are used as MOX sensors are SnO₂, as used in the sensor array 6 ofthe device 2 described hereinabove. The SnO₂ sensors can be enhanced,selectivity wise and sensitivity wise by the use of catalytic additives,such as the Pt present in sensors 12′ and 12′″ of the device 6.

The resistance change induced by the sensors is caused by loss or gainof the surface electrons as a result of absorbed oxygen reacting with atarget gas. If the oxide is an n-type, there is either a donation(producing gas) or subtraction (oxidizing gas) of electrons from theconduction band within the material. The result is that n-type oxidesincrease their resistance when oxidizing gases such as NO₂, O₃ arepresent while reducing gases such as CO, CH₄, and ethanol lead to areduction in the resistance. The converse is true for p-type oxides,where electron exchange due to gas interaction leads either to a rise(oxidizing gas) or a reduction (reducing gas) in electron holes in thevalence band. Each of these reactions then translates into correspondingchanges in electrical resistance. Unlike some of the gas sensingtechnologies, MOX sensors can be made quantative, as the magnitude ofchange in electrical resistance is a direct measure of the concentrationof the target gas present.

The sensors 12, 12′, 12″, 12′″, were selected due to their advantageousproperties in detecting NO₂, O₃, CO, CH₄ and ethanol, as are commonlyproduced as gases through smoking tobacco. Thus the device 6 whichutilizes the sensor materials given above is particularly suited tosensing gases produced in tobacco smoking in a confined or semi-confinedairspace.

Since the change in electrical resistance in the sensing oxide ofsensors 12, 12′, 12″ and 12′″ is caused by surface reaction, it isadvantageous to maximize the surface area to intensify the response tothe gas. For this reason, the sensors 12, 12′, 12″ and 12′″ include alayer of MOX material 20 which is in the form of a thin film.Alternatively the layer 20 may be slightly thicker, but highly porous.The MOX material 20 is either printed down or deposited onto thesemi-conductive layer 16. The electrodes 18, 18′ are coplanar andlocated at the MOX material 20/semiconductor layer 16 interface. In thesensor array 6 shown in FIG. 2, the SiO₂ insulating layer 16 isapproximately 1 μm thick. The Ta/Pt inter-digital electrodes 18, 18′ areapproximately 200 nm thick but may be anywhere between 10 nm and 1000 nmthick.

Selectivity can be enhanced further if desired through the use ofdifferent metal oxide layers 20 in each of the sensors, or use ofcatalytic additives, different operation temperatures, protectivecoatings and activated carbon filters, for example.

Upon detection by the sensors 12, 12′, 12″ and 12′″, and upon loweringof the resistance as shown in FIG. 4, the sensor array 6 emits a signalvia electrical circuit 7 to the canister 8 to effect dispensing of aportion of the deodorizing agent within the canister. Upon receipt ofthe signal, a pump (not shown) within the canister 8 actuates to pump aportion of the deodorizing agent through the outlet conduit 11 andthrough the nozzle 10 of the device 2. As the canister 8 pumps out theportion of a treatment agent, the fan 14 is actuated. Thus as the agententers the nozzle 10, the fan effects increased dispersion of the agentfrom the nozzle 10 through the apertures (not shown), such that thespray or mist of the treatment agent reaches further into the airspacein which the device 2 is situated.

In use the air treatment device 2 is located within an airspace to betreated, such as a room, refrigerator, sanitary bin, sharps bin or thelike etc.

Use of the device 2 will now be described by way of an experimentalexample. The device 2 was utilized in a living a room of a two personhousehold, where tobacco smoking took place.

The device 2 was mounted to a wall within the living room of a householdin Hessle, UK, and activated to detect a combination of gases producedin combustion of tobacco through persons in the room smoking cigarettes.

In particular, the sensor material 20 of the sensors 12, 12′, 12″, 12′″of the device 6 are able to detect NO₂, O₃, CO, CH₄ and ethanol, whichare common gases produced through combustion of tobacco.

The device 6 was activated, and a person entered the room at apredetermined time 9.30 am, and lit a cigarette. Approximately 2½ hourslater a second cigarette was lit within the room by the same person.FIG. 4 shows the output results of the four sensors 12, 12′, 12″, and12′″, in response to detection of gases produced by the cigarette smokewithin the airspace. As can be seen from FIG. 4, as the first cigarettewas lit at 9.30 am, the sensors 12, 12′, 12″ and 12′″ recorded adecreasing resistance across the sensor material 20. When the secondcigarette was lit at 1.10 pm, again the four sensors 12, 12′, 12″ and12′″ recorded a decrease in resistance across the sensing material 20.

Upon detection by the sensors 12, 12′, 12″ and 12′″, and upon loweringof the resistance as shown in FIG. 4, the sensor array 6 emitted asignal via electrical circuit 7 to the canister 8 to effect dispensingof a portion of the deodorizing agent within the canister. Upon receiptof the signal, a pump (not shown) within the canister 8 actuated to pumpa portion of the deodorizing agent through the outlet conduit 11 andthrough the nozzle 10 of the device 2. As the canister 8 pumped out theportion of a treatment agent, the fan 14 was actuated. Thus as the agententered the nozzle 10, the fan effected increased dispersion of theagent from the nozzle 10 through the apertures (not shown), such thatthe spray or mist of the treatment agent reached further into the livingroom in which the device 2 was situated.

FIG. 5 shows the results of a second experiment in which the device 6was placed in a second living room at a household in Freiburg, Germany.Three cigarettes were smoked during the day at 11.10 am, 11.45 am and7.25 pm. The device 2, for this experiment, was utilised with only twosensors, 12 and 12′, corresponding to the SnO₂/Pt and SnO₂ materials assensor material 20. It can be seen that immediately upon lighting acigarette at 11.10 am, 11.45 am and 7.25 pm resistance was loweredacross the MOX material 20 of the sensors 12 and 12′, which induced asignal, which was subsequently emitted via the control circuit 7 to thecanister 8. The canister 8 then actuated release of a portion ofdeodorizing air treatment agent out of the device 2 via the nozzle 10 asdescribed herein before, in order to mask the tobacco gas malodour.

Thus the device 2 can be used effectively to counter malodour producedby tobacco smoking or other malodour produced within a confinedairspace. Sensor 2 may be situated in any confined or semi-confinedairspace where malodours occur. The sensor material 20 may be changed toincrease selectivity and/or sensitivity to varying gases which may beproduced as part of a malodour.

In alternative embodiments, instead of MOX sensor material, conductingpolymer (CP) sensors may be utilised. There are a number of potentialadvantages in using conducting polymers, over the other sensortechnologies, for vapour sensing. There is a far wider choice ofmaterials and hence functional groups with which the vapour caninteract, and the materials are often easier to process than inorganicmaterials, i.e. metal oxides. Some conducting polymer sensors canoperate at room temperature, which is a distinct advantage over thesemiconductor MOX sensing technique, as there is an inherent low powerrequirement. They also show reversible characteristics at roomtemperature, this means that the recovery rate of the sensors afterexposure to target compounds is better than SAW (Surface Acoustic Wave)sensors. The electronic control of the sensor is far less complicatedthan both semiconductor MOX and SAW detection. The CP sensor is stableup to 40° C. and 90% humidity, which is the most significant advantageover the sensing techniques.

The conducting polymer sensors are essentially two gold microelectrodeswith an insulating gap between them. The conducting polymer is grownelectrochemically across the gap to form the sensor. The conductivity ofthe polymer is altered by the presence of nucleophilic and electrophilicgases which results in a decrease and increase in conductivityrespectively. Therefore by following the resistance between the twomicroelectrodes the sensors can be used to sense gases and vapours. Thepolymers may be doped with anions such as Cl⁻ and So₄ ²⁻, which canalter the sensitivity to different vapours.

The conducting polymer, once coated onto the electrode material,requires activation before use as a chemical sensor. Activation isrequired to convert the insulating, neutral form of the polymer tooxidized, positively charged, conducting form where anions from anelectrolyte solution are incorporated into the polymer film. To achievethis the polymer films are first characterized in a base electrolyte byanother electrochemical process called cyclic voltammetry. Here thepotential is cycled between certain limits at a chosen scan rate for atleast two complete cycles. The point at which an oxidation peak occursgives the maximum potential required for activation, and potentialsabove this which cause over oxidation and degradation of the conductingpolymer film.

Other gas detectors that may be used alternatively or additionally toMOX and CP based gas detectors include those comprising Surface AcousticWave sensors and/or sensor materials.

In further embodiments the portion of dispensing agent dispensed upondetection of a gas or plurality of gases by the sensor array 6 maycomprise a plurality of intermittent pulses, whether at regular orirregular time intervals, or may comprise a continuous dispersal of astream of air treatment agent over a defined period of time. The definedperiod of time may be user defined or preset in the device 2. The device2 may emit a constant background level of air treatment agent and expela portion, in the form of a booster portion upon detecting an airborneagent in an airspace.

The device 2 may include a heater, in other embodiments, in addition toor alternative to the fan 14. The heater may be arranged to render anyair treatment agent expelled through the nozzle 10 more fluid orvaporize a liquid air treatment agent. The heater may even activate airtreatment agents which comprise heat-activated compounds. Other airtreatment agent expulsion means may include nebulisers, electrostaticmeans, a simple wick or the like for example.

In yet further alternative embodiments the portion of air treatmentagent to be dispensed may be effected to be dispensed immediately upondetection of a gas, or at any defined time interval after detection of agas. The fan 14 may be effected to continue operation after the portionof air treatment agent has been dispensed, in order to further encouragethe air treatment agent to disperse around the airspace after the device2 has been activated.

The device 2, may comprise, instead of a gas detector, a detector in theform of a biosensor or chemical sensor. The biosensor or chemical sensormay be arranged to detect a particulate solid, liquid or gas in air, andmay be arranged to detect chemical agents or biological material such asproteins, microorganisms, allergens, fungal spores and the like forexample. The biosensor or chemical sensor may be any suitable sensorsuch as an amperometric sensor, optical sensor, or the like, forexample, as are well known to those skilled in the art.

Further experiments were carried out with a device comprising foursensors, namely: SnO₂; [SnO₂+Pt] (in series); CTO(Cr_(1.8)Ti_(0.2)O_(3+z)); and WO₃. All were set on a common siliconwafer, on a common quartz substrate.

The target gases were H₂S, (CH₃)₂S and CH₄S. The tests were carried outunder ambient conditions, with the usual heating of the sensors.

FIG. 6 shows the change in resistance across the CTO, SnO₂ and [SnO₂+Pt]sensors (R=resistance; Ro=original resistance) at concentrations of 2ppm, 5 ppm and 10 ppm of (CH₃)₂S. The CTO and [SnO₂+Pt] sensors appearto be particularly discriminating.

FIG. 7 shows corresponding results for CH₄S at concentrations of 0.1ppm, 0.2 ppm, 0.5 ppm and 1 ppm by volume. In the case of this gas theCTO and SnO₂ sensors appear particularly discriminating.

FIG. 8 shows corresponding results for H₂S at concentrations of 0.1 ppm,0.2 ppm, 0.5 ppm and 1 ppm by volume. In the case of this gas, all thesensors tested appeared to be discriminating.

Tests were also carried out on the unit for which results are given inFIGS. 6 to 8, but using CO, NO₂ and NH₃, in turn, as the gas. These areregarded in this example only as interfering or rogue gases in thecontext of detecting the target gases; it is not wished that theytrigger release of airborne agent in this example. It was found thatthey gave a small change in sensor resistance at normal levels; suchthat they would not release of airborne agent. If necessary a sensor“tuned” to CO, NO₂ or NH₃ could be provided, such that if that sensorfired, the device either would not trigger the release of airborneagent, or would only do so if an especially high level of H₂S, CH₄s or(CH₃)₂S was detected.

1. An air treatment device comprising: a gas or vapour detectorcomprising a plurality of gas or vapour sensors, wherein the gas orvapour detector comprises means to detect a threshold level orconcentration of a gas or vapour; a means to mount a source of airtreatment agents to the device; and a means to expel a portion of airtreatment agent, upon detection of a gas or vapour by the detector. 2.An air treatment device according to claim 1 wherein the mounted sourceof air treatment agent also passively emanates the air treatment agent.3. An air treatment device according to claim 1 wherein the means toexpel a portion of air treatment agent comprises a heater element inproximity to a diffusion wick, the heater element being actuated upondetection of a gas or vapour by the detector in order to increase theemanation of the air treatment agent.
 4. An air treatment deviceaccording to claim 1, wherein the means to mount a source of airtreatment agent to the device comprises means to connect a receptacle(8) to the device, the receptacle (8) comprising the air treatmentagent.
 5. An air treatment device according to claim 1, wherein thedevice includes a processor unit to determine when the signals from thegas or vapour sensors (6) cause expulsion of a portion of air treatmentagent.
 6. An air treatment device according to claim 1, wherein thedevice comprises at least two sensors which sense the same gas or vapourand the processor unit receives signals from both sensors in order tocause a portion of airborne treatment agent to be expelled.
 7. An airtreatment device according to claim 5, wherein the detector includes asensor which detects both a target gas or vapour and a non-target gas orvapour, wherein in order to eliminate expulsion of air treatment agentin response to the non-target gas or vapour, the device includes asecond sensor which detects the non-target gas or vapour but not thetarget gas or vapour, the processor unit being arranged to preventexpulsion of the air treatment agent when the second sensor detects asignal, completely or until the first sensor gives a signal at a higherthreshold value than usual.
 8. An air treatment device according toclaim 5, wherein the detector includes a person detector, and theprocessor unit allows airborne treatment agent to be expelled, inresponse to a signal from one or more of the sensors, only when theperson detector gives a signal and for an interval thereafter.
 9. An airtreatment device according to claim 1, wherein the detector comprises aconducting polymer sensor.
 10. An air treatment device according toclaim 1 comprising at least one metal oxide sensor.
 11. An air treatmentdevice according to claim 1, wherein the air treatment agent expulsionmeans comprises a pump or aerosol.
 12. An air treatment device accordingto claim 1, on which is mounted a source of air treatment agent.
 13. Anair treatment device according to claim 1, wherein the air treatmentagent comprises an agent capable of masking, neutralising or retardingmalodour, or unwanted odour.
 14. An air treatment device according toclaim 1, wherein the air treatment agent comprises a deodorant, ananti-bacterial agent, a sanitizing agent, a fragrance, a perfume or ananti-allergenic agent.
 15. A method of treating an airspace with an airtreatment agent, the method comprising the steps of: providing an airtreatment device according to claim 1, and detecting a gas or vapour inan airspace and activating expulsion of an air treatment agent into theairspace in response to detection of the gas or vapour, using an airtreatment device.
 16. The method according to claim 15, comprising thefurther step of expelling a single portion of agent in response todetection of an airborne agent, or a plurality of portionsintermittently.
 17. The method according to claim 15, wherein expulsionof an agent comprises expelling a continuous stream of agent for adefined period of time upon detection of an airborne agent.